It is known in the art to shrink form containers such as drinking cups from preformed tubular lengths of circumferentially oriented thermoplastic material such as foamed polystyrene.
One particularly desirable method of initially forming a tubular length of such circumferentially oriented material is to provide rectangular-preprinted blanks and wrap these blanks around a mandrel whereon a heat sealed seam is effected longitudinally along the circumference of the formed tubular length. The use of rectangular blanks facilitates pre-printing of patterns, designs, logos, etc. on the blanks such that the ultimate tubular lengths and containers formed therefrom will bear the ultimately desired indicia.
A further advantage of the rectangular blank is that it may be cut from an extruded sheet of thermoplastic or thermoplastic foam which is stretched longitudinally, i.e., in the most logical, natural and facile direction of stretch after extrusion, namely, the machine direction, to achieve the necessary circumferential orientation in a tubular length or cylinder formed from the rectangular blank.
Previous efforts to handle these rectangular blanks and form them into cylinders, however, have required relatively elaborate systems of transfer rollers, turrets with multiple mandrels thereon and vacuum systems to properly index leading and/or trailing edges of the rectangular blanks on the transfer rollers or mandrels.